1. Field of the Invention
The present invention relates to a method for mobile robot motion control, and more particularly to a method for mobile robot motion control suitably used for controlling movements in the robot in the case where a human being (operator) and the robot manipulate a single object in cooperation with each other.
2. Description of the Related Art
In general, robots have been developed in a fashion wherein they assist working which have been performed heretofore by human workers in large-scale facilities, and industrial plants such as principally chemical plants, nuclear power plants, or a variety of outdoor or indoor job sites.
In this respect, it has been presupposed that workers do not go into a job site where robots operate during their working in view of safety. Based on such presupposition, a variety of robots are constituted.
On one hand, it is expected to apply robot for new fields such as medical and welfare job sites or domestic service, because of developments of robot technology in recent years. In such medical and welfare job sites or home and the like, it is considered that there are many scenes where human being and robot coexist and act together in the same working space, and human being works in cooperation with robot.
In these circumstances, when it is intended to fix up robot for use in a factory and the like, no mobile mechanism or the like is required for such robot. In the other cases, however, i.e., the cases where robot is used in medical and welfare job sites or home and the like as described above, it is indispensable to prepare a mobile mechanism by which robot can freely move in such sites.
In this respect, when it is considered to use robot in medical and welfare job sites or home and the like, it becomes a problem to provide such mobile mechanism as described above on a considerably large robot in view of safety. Accordingly, it has been needed that such mobile mechanism as described above is applied to a comparatively small-sized robot, and such a robot who can move in a space where the robot itself presents (a robot provided with a mobile mechanism by which the robot can move freely in a specified space where the robot itself presents is herein referred optionally to as xe2x80x9cmobile robotxe2x80x9d) is cooperatively utilized with respect to human being, whereby human being and robot can work in cooperation with each other.
The present invention has been made in view of the need as described above, and an object of the invention is to provide a method for controlling movements in a mobile robot which can manipulate an object in cooperation with human being.
In order to achieve the above described object, a method for mobile robot motion control according to the present invention is constituted in such that a load in its gravitational direction is compensated totally by a mobile robot with holding an object thereby, while a human being gives a motion command with respect to the mobile robot to travel the same in a desired orientation, whereby the object is manipulated. It is very effective to control motion of mobile robot by human being""s motion command.
It is studied herein a case where a human being works cooperatively with a mobile robot, the following two tasks must be carried out in the case where a single object is manipulated by the human being in cooperation with the mobile robot.
One of the tasks is a positioning task wherein a position and a posture of the object are determined correctly and arranged suitably, and another task is a conveying task for conveying the single object to a certain target point.
In the positioning task, it is preferred to be capable of controlling the mobile robot in such that the object is moved on the basis of a force applied to the object by the human being and its orientation decided by the human being, while it is preferred in the conveying task to be capable of controlling the mobile robot in such that the object is moved in only the travel orientation thereof decided. According to such arrangement as described above, the object can be manipulated while reducing a burden of the human being.
According to the present invention, a method for controlling mobile robot by which it becomes possible to conduct the above described positioning task and conveying task in the mobile robot is realized.
Namely, a method for mobile robot motion control according to the present invention provides a manner for controlling mobile robot in a control system for manipulating a single object by a human being in cooperation with mobile robot.
More specifically, the present invention provides a manner wherein a manipulating task for a single object is classified into two tasks of a positioning task and a conveying task, and characteristics of a caster is given to the mobile robot in order to reduce human being""s burden in these two tasks.
In the section xe2x80x9cDetailed Description of The Preferred Embodimentxe2x80x9d which is mentioned hereinafter, experimental results in the case where a manner of the method for mobile robot motion control according to the present invention is applied to an omnidirectionally mobile robot, whereby the mobile robot manipulates a single object in cooperation with a human being are shown, and as a result, it has been found that effectiveness of the present invention becomes clear.
Accordingly, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that the motional characteristics of the mobile robot are made to be virtually equivalent to motional characteristics of a caster, whereby motional performance adaptable to an external force is realized.
Furthermore, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that characteristic parameters of a caster are dynamically changed in control for mobile robot to which have been virtually applied equivalent motional characteristics of the caster, whereby motional characteristics of the mobile robot are appropriately changed.
Thus, according to the subject inventions, a cooperative manipulation of a single object by which a burden share of human being is reduced can be realized.
Moreover, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that a control parameter ri is made to be small in the case where a speed of a mobile robot in its travel orientation is low, while the control parameter ri is made to be large in the case where the speed of the mobile robot in the travel orientation is high; and the control parameter ri is an offset defined between a moving center of the mobile robot and a holding point at which the robot holds an object.
Furthermore, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that a control parameter tranDi is made to be large in the case where a speed of a mobile robot in its travel orientation is low, while the control parameter tranDi is made to be small in the case where the speed of the mobile robot in the travel orientation is high; and the control parameter tranDi corresponds to the origin of a robot coordinate system rxcexa3i fixed to a holding point of the mobile robot, at the same time, it is allowed to coincide a cxi-axis of a caster coordinate system cxcexa3i rotatable freely around the origin with its travel orientation of the mobile robot, and it corresponds to a positive damping coefficient in the case where the mobile robot is subjected to damping control based on a force cfxi acting in the cxi-axial direction.
Moreover, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that a control parameter rotDi is made to be small in the case where a speed of a mobile robot in its travel orientation is low, while the control parameter rotDi is made to be large in the case where the speed of the mobile robot in the travel orientation is high; and the control parameter rotDi is a positive damping coefficient in the case where the mobile robot is subjected to damping control by a moment acting upon the mobile robot.
Furthermore, the subject invention relates to a method for mobile robot motion control for the sake of controlling motional characteristics of the mobile robot, characterized by that a control parameter ri is made to be small, a control parameter tranDi is made to be large, and a control parameter rotDi is made to be small in the case where a speed of a mobile robot in its travel orientation is low, while the control parameter ri is made to be large, a control parameter tranDi is made to be small, and a control parameter rotDi is made to be large in the case where the speed of the mobile robot in the travel orientation is high; the control parameter ri is an offset defined between a moving center of the mobile robot and a holding point at which the robot holds an object; the control parameter tranDi corresponds to the origin of a robot coordinate system rxcexa3i fixed to a holding point of the mobile robot, at the same time, it is allowed to coincide a cxi-axis of a caster coordinate system cxcexa3i rotatable freely around the origin with its travel orientation of the mobile robot, and it corresponds to a positive damping coefficient in the case where the mobile robot is subjected to damping control based on a force cfi acting in the cxi-axial direction; and the control parameter rotDi is a positive damping coefficient in the case where the mobile robot is subjected to damping control by a moment acting upon the mobile robot.
It is to be noted herein that motional characteristics of a mobile robot change dependent upon the control parameter ri, the control parameter tranDi, and the control parameter rotDi, respectively.
Therefore, when the parameter ri, the parameter tranDi, and the parameter rotDi are determined on the basis of the travel speed of a mobile robot as in the subject inventions, a cooperative manipulation of a single object by which a human being""s burden share is reduced can be realized.
Moreover, the subject invention relates to a computer-readable storage media, characterized by that a program for executing a method for mobile robot motion control as mentioned above by a computer is recorded therein.